Originally Posted by Scottish XF

Before parking the car at night, I put the windows down and turn off the heater for the last couple of minutes of the journey. This cools the inside of the car down a lot (although freezes you in the process) and makes any temperature change a lot smaller when you've locked the car, thus avoiding the same amount of condensation / fog forming on the windows.

Also, as per the other post in the forum just now on fogging, make sure you give the windows a good clean to avoid moisture clinging to the dirt.